Hmmm...it now runs an interactive environment now. Nice touch. However, I can't start the gui anymore:

> calibre-debug -g
Traceback (most recent call last):
File "/Applications/calibre.app/Contents/Resources/loaders/calibre-debug.py", line 12, in <module>
main()
File "/Users/jim/Projects/Calibre/calibre/src/calibre/debug.py", line 163, in main
from calibre.gui2.main import main
File "/Users/jim/Projects/Calibre/calibre/src/calibre/gui2/main.py", line 15, in <module>
from calibre.gui2.ui import Main
ImportError: No module named ui